Passive elements are needed in RF SOI and RF power amp applications. Inductors may be formed in a substrate, for example, to enable designers to integrate high-Q resonant circuits in support of, e.g., low-phase-noise voltage-controlled oscillators (VCOs), narrow-band filters, and low-loss impedance matching. More specifically, a trench may be formed in a substrate and a conducting material, for example, may be deposited in the trench to form the inductor. Conventionally, a substrate may have a resistance on the order of two to twenty Ohm-cm. Thus, an additional insulator layer or film is formed in the trench between the substrate and the inductor to insulate the inductor from the substrate. The formation of the insulating layer is an additional process that adds to the costs of the manufactured device.
Devices in advanced microelectronics employ silicon-on-insulator (SOI) technology for improved performance, where the active area of a device is in a thin silicon layer, isolated from the bulk silicon substrate by a buried oxide (BOX) layer. The BOX layer provides electrical isolation from the substrate for improved field distribution in the active area. The implementation of SOI technology is one of several manufacturing strategies employed to allow the continued miniaturization of microelectronic devices.
SOI technology utilizes ultra high resistivity wafers, having a resistance, for example, from one to ten k-Ohm. However, known methods and devices having buried inductors include an insulating layer between the buried inductor and the ultra high resistivity wafer, and do not fully utilize the SOI ultra high resistivity wafers' properties.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.